Electric and pneumatic powered hand tools are commonly used on assembly lines and assembly stations in industrial manufacturing settings. These tools include drivers for bolts, nuts, screws and like fasteners. While some manufacturing techniques are adaptable to robotic systems, many utilize an operator wielding a powered hand tool. The assembly of a work piece typically involves numerous steps and includes a multiplicity of riveting, threading, and tightening various types of fasteners usually in a particular order and in a three dimensional space around the work piece. Thus it is not uncommon for dozens of differing types and sizes of fasteners to be installed on a particular job with the requirements that the installation and tightening of the fasteners must be in certain prescribed order, or else the stress placed on the parts by tightening a fastener out of order might induce a crack or other failure. Rigorous training is required to attempt to control the operator and reduce the chance of error. However, mistakes occur resulting in breakage during manufacture or later failure due to stresses placed in the part by incorrect installation during manufacture. The prior art has failed to successfully address these problems.
Optical encoder devices that digitally measure an angular position have been used in industrial manufacturing applications, most notably in robotic controlled and operated systems. However, these devices have not been used to attain the objects described herein below and in the present invention.
Present power tool balancers and anti-torque tool holding devices have inadequate balance control effectiveness and allow substantial torque feed back to the operator when the tool is in some positions. For example, when the tool is supported on an arm that includes a plurality of universal joints, each of which allows rotational movement in one plane, alignment of the torque at certain angles with these planes can result in some torque feedback to the operator. Spring loaded balance mechanisms are commonly used tool suspension apparatuses, but these are difficult to control and adjust to changing conditions such as the weight of the tool and individual operator preferences. Some operators prefer that the system require some lifting of the hand-tool and others prefer that some pulling down of the tool against the spring tension be required for operation. Since operators change at the end of shifts and sometimes during the shifts, adjustment is cumbersome, at best time consuming and may not be available at all.
U.S. Pat. No. 5,791,619 to Myers discloses an anti-torque tool suspension arm using a splined axially extensive arm in and axially extensive housing cavity with a splined hub insert to “largely eliminate play between the rod and housing”. U.S. Pat. No. 6,054,373 to Watanabe, et al. discloses a power tool holding assembly that includes piston-cylinder linear movement guiding unit with a ball spline with a piston rod. U.S. Pat. No. 5,213,292 to Evans discloses a tool balance using springs. U.S. Pat. No. 5,580,021 to Gillanders discloses a suspension mechanism for a hand-manipulated power-tool wherein the suspension tension is relieved when the tool is actuated. U.S. Pat. No. 5,109,736 to Dixon discloses power screwdriver on a cantilevered support movable on a worktable with power assist up and down. U.S. Pat. No. 5,544,554 to Brightly discloses a pneumatic torque wrench mounted on a torque arm, which is locked in place when the wrench is engaged allowing the operator to remove hands when the torque is applied. U.S. Pat. No. 6,324,728 to Blankenheim discloses an ergonomic attachment for inline power tools that includes an inverted U-shaped member that is forced downwardly on the forearm of the operator.
None of these devices satisfy the needs addressed herein and satisfy the objects of this invention.